Heater



Dec. 22, 1942.

M. FRlscH 2,305,611

HEATER Filed July 3l, 1940 3 Shees-Sheet l TM* .f /0 g o o o o a o o o o o o Q f o lf3 23" f .l HULMJMM 'hl-24 l E r Y l/ *"J/ z 11% r zz M* W i TWP .L= r @QZ 36' 22 .1 4 r 1 /f-a Dec. 22, 1942. M. FRlscH 2,305,611

HEATER Filed July 31, 1940 3 Sheets-Sheet 3 INVENTOR Patented Dec. 22, 1942 2.30am naam Martin Frisch, New York, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application July 3l, 1940, Serial No. 348,793

20 Claims.

This invention relates to fluid heaters including vapor generators, and more particularly pertalns to steam generators of the type having a setting or the like which is divided by one or more vertical division walls or partitions to provide the generator with two or more separate furnaces adapted to be independently fired and to operate in parallel. In furnace arrangements of this kind, inner surfaces of the walls of the furnaces ordinarily are lined with heat absorbing means such as water wall tubes, and some of the wall surface of one or more of the furnaces may contain radiant heat superheater tubes. The division wall between adjacent furnaces frequently includes two closely spaced parallel rows or groups of tubes, which are secured together by common tie members, and refractory material is disposed in the space between the rows, the arrangement being such that each row of tubes will be directly exposed tothe products of combustion produced in only one of the furnaces, and the heating gases will flow through the two furnace chambers in separate paths. When the furnaces are fired unequally, those tubes lining the wall surface of the furnace which is more intensely fired, will expand more than the tubes on the walls of the furnace which is less intensely fired, so that there will be relative movement between the tube rows due to the different furnace temperatures.

The present invention provides supporting means for steam generator furnace division walls having fluid cooling tubes associated therewith, which will support the tubes adequately under all operating conditions and will permit relative movement between rows of these tubes as required, without distortion or other movement thereof.

The invention will be understood from the following description when considered in connection with the accompanying drawings forming a part thereof, and in which:

Fig. l is a partial vertical sectional view of one form of steam generator embodying the invention;

Fig. 2 is an enlarged partial vertical sectional view of part of the generator shown in Fig. 1;

Fig. 3 is a vertical sectional view taken on line I-l of Fig. 2;

Fig. 4 is an enlarged vertical elevational view of a detail of the generator;

Fig. 5 is a transverse sectional view taken on line 5-5 of Fig. 4;

Fig. 6 is a vertical elevational view taken on parts in the several views.

Referring to the drawings, particularly Fig. 1, reference character III designates generally a steam generator having a setting which includes a front wall II. a rear wall not shown, and side walls I2 and I2. Midway between the side Walls is a vertical division wall which comprises two spaced rows or groups of vertical tubes I4 and I5 and refractory material It built up between the rows of tubes. This division wall extends across the setting from the front wall to the rear wall, and provides two separate furnace chambers I1 and I il, which are independently fired by fuel burners Il and 20 respectively, disposed in front wall I I. Groups of closely spaced water wall tubes 2i and 22 which are connected at their upper ends to headers 22 and 24, and at their lower ends to headers 25 and 2B respectively, line the iront wall, and similar groups of water wall tubes not shown, line the rear wall of the setting. The side wall I2 is lined with water wall tubes 2l which are connected to upper and lower headers 2l and 28 respectively, and are connected into the circulatory system of the generator. The side wall Il is lined with radiant heat absorbing superheater tubes 30 which are alternately connected at their upper ends to inlet and outlet headers 2i and 32 respectively, and at their lower ends to a return header 33. The groups of water wall tubes 2|, 22 and 21, and the superheater tubes 30, are secured to the respective setting walls by tie back members 34 which form no part of the present invention and need not be described in detail. In addition lto the water Wall tubes 2l and 22, another group of shorter water wall tubes 35 line that part of the front setting wall which is adjacent the division wall, and are suitably connected into the circulatory system. A similar group of tubes not shown, is disposed in the rear wall of the setting. Any suitable means are employed to secure the water wall tubes in position and in such manner that they may expand and contract `with respect to the wall to which they are attached.

In the form shown, the upper ends of the division wall tubes I4 and- I5 are connected to a drum 36 which is suitably supported on or from the setting and which serves to support or suspend these tubes together with the refractory material I8 which is inserted between them. At

their lower ends the tubes I 4 and I5 are connected to headers 31 and 38 respectively. The lower portions of each of the side walls of the furnaces I1 and Il are inclined inwardly in such a way as to provide each furnace with a water cooled hopper bottom.

As clearly illustrated in Figs. 2, 4, and.6, the two rows oi' the division vwall tubes are secured to each other in the desired spaced relationship by means disposed between the tube rows. Buch means includes tie members 4I which are supported on upper lugs 34 and lower lugs 40 which are welded to the tubes I5 and I4 respectively in spaced relationship. The tie members 4I are provided with spaced apertures in alignment with the tubes, and each tie member is of such length as to extend transversely of a plurality of tubes. The apertures in the upper and lower lugs are in axial alignment with each other, and are adapted as are the apertures in the tie members to freely receive pins 42, which are provided with heads 43 to hold the pins in place. This securing means will permit relative vertical movement between the tubes I4 and I5, and will maintain the tubes of each row and the two rows in proper spaced relationship.

Below the vertical portion of the division wall, the groups of tubes I4 and I5 are oppositely inclined to form walls for the hopper bottoms of the adjacent furnaces. Adjacent the hopper discharge point of each furnace, the tubes of each group are bent to extend horizontally in oppQsite directions towards the center line of the setting before entering the headers 31 and 38 respectively. These headers are carried by a plurality of separate spring supports, each of which includes a. spring 44 housed in a. casing 45, and which rests on a foundation 45. Between the headers and the springs 44 are saddles or brack- 35 ets 41, and between the latter and the upper emitt of each spring is a transverse plate 48 (Fig. 3). Extending between the ends of each plate 48, and lugs 49 which are ilxed to the walls of the casings 45, are rods 58 havingxed thereto upper and lower fixed stops 5I and 52 and which are secured at their upper ends to the plates 48. The arrangement is such, that as the springs are depressed or as they expand in response to vertical movement of the headers 31 and 38, the rods 58 will slide through apertures 53 in the lugs 49 and the amount of this vertical movement is controLed and limited by the stops 5I and 52 on the rods 55.

Immediately above the headers 31 and 38, the oppositely inclined hopper sections of the division wall tubes and the refractory portions 54 and 55 of the hopper walls are carried by a steel supporting structure, which as viewed in Figs. l. and 2, is of a generally triangular shape. Referring particularly to Figs. 2, 3 and 10, gusset plates 55 and 51 which form the apex of this structure extend the length `of the setting and are bolted together, the bolt holes in the plate 55 being elongated to permit limited relative movement between the plates vertically. A woven asbestos gasket 51 separates the plates 58 and 51. A plurality of angle members 58 and 59 (Fig. 10) are secured to the plate 55 and a plurality of similar angle members 55 and 5I are secured to the plates 51. 'I'he angles 58 and 59 support a casing section 52, while the angles 58 and 6I support casing section 53. The refractory portions 54 and 55 of the hopper walls are enclosed between the casing sections 52 and 53 respectively and the tubes. The angle members 58 and 59 have secured to their lower ends, a member 54 which is connected to a member 55 which rests upon and is connected to the header 31. The angle members 59 and 8l are similarly connected to members 85 and 51 and the header 38. The upper portion of the casing section 52 extends parallel with the inclined portions of the tubes I4 and the lower portion extends vertically-downward to the foundation of the setting. The tubes I4 pass through the casing as indicated at 55 y and 58, suitable means being provided to permit relative movement of the tubes and the casing at these points. The casing section 53 and the tubes I5 are similarly arranged. A plurality of horizontal tie members 19 extend between the lower ends of the angle members 53, 59 and 59, 5I. The tie members are secured by pins at their ends to the angle members by brackets 1I, a pin and slot being utilized at one end of each tie member to permit limited relative movement with respect to one group of angle members.

The greater part of the weight of the refractory portion of the division wall and the casing structure described is supported by two heavy parallel, fixed beams or girders 12 and 13, which extend longitudinally of the setting for the length thereof. Extending between the beams andtransversely thereto are a plurality of pairs of channel members 14 which rest on the lower flanges 15 and 15 respectively of the beams. Supported by the channel members are a plurality of spring supports, which are somewhat similar to the spring supports described in connection with the headers 31 and 38. These spring supports have a circular bottom plate 11 (Fig. 3) in which isa centrally disposed aperture 18, and a rod 19 which slides freely in this aperture and extends vertically through a spring and through an upper plate 8| which rests on the upper end of the spring. A stop 82 carried by the rod bears against the upper face oi plate 8l, and the upper end of the rod is secured between a pair of channel members 84 by a pin 83 which passes through an aperture in the rod or in an extension thereof. This connection is so arranged that the channel members 84 may oscillate about the pin 83 within the limits permitted by the entire structure. Otherwise the structure and operation of these spring supports are similar to those previously described for the support of the headers 31 and 38. The channel members 84 extend transversely between the casing angle members 58, 59 and 50, 5I to which they are connected at their ends by pins 85 (Fig. 7) in such manner that the members 84 may move in vertical planes to a limited extent in either a clockwise or counter-clockwise direction, and any such movement will be against the action of the spring supports.

Roller bearing means are provided to permit vertical movement of the casing sections with respect to the fixed beams 12 and 13. Secured to the upper flanges 85 of the beam 12 is a longitudinally extending angle member 88, and

secured to the upper flange 81 of the beam 13v o and the member 88, and in contact therewith,

are rollers 92. Similar rollers 93 are disposed between the bracket 9I and member 89. Suitable means are provided to confine the rollers 92 and 93 to their bearing surfaces. Fixed to the lower portions of the casing sections 62 and 13 and to the tie members 10, are a plurality of brackets 94 and 95 respectively. Fixed to the brackets 94 or to other parts of the casing section 52, is a longitudinally extending beam 96, and a beam 91 asoman is similarly arranged with respect to the brackets l or the casing section 00. Between the inner flange 00 of beam 00 and the beam I2 are a plurality of roller guide brackets 0I within which are rollers |00. Between inner flange |0| of beam 01 and beam 10 are similarly disposed a plurality of roller guide brackets |02 which house rollers |03. It willbe apparent that this roller bearing arrangement will permit vertical movement ,of either or both of the inner hopper walls with respect to the supporting means therefor upon expansion and contraction of the division and hopper wall tubes.

In the hopper walls adjacent the gusset plates Il Aand 01, tube securing means are employed which permit relative movement between the tubes Il and II, the adjacent refractory portions 04 and Il of the hopper walls. and the steel casing sections 02 and l0 respectively. As clearly shown in Figs. 8, 9 and 10 of the drawings, rectangular plates or lugs |04 are welded to the peripheries of the tubes at spaced points along the wall sides thereof. These plates are received within spaces lll between closely spaced hollow blocks or backing members |00 which are T- shaped and have solid projections |01 that are securely locked between the flanges of opposed channels |00 and |00. The lower channel |00 of each receiving means is supported by an angle member ||0 which is secured by bolts to the casing section and the upper channel |00 rests upon the projections |01 and upon a plate ||2 which rests upon the angle member I|0 and the casing section. The channels |00 and |00 and the angle members I I0 extend transversely of the tubes for the length of the furnace setting. A plate ill covers the joints between the lugs |04, the members |00 and the upper angle member |00. The securing means just described is utilized at the upper portion of each hopper bottom on both sides thereof. Similar securing means are employed at the lower portions of the hopper bottoms on both sides thereof, the only essential difference being that the angle member ||0 is not used, but the lower channel |00 rests upon the refractory.

In operation, the division wall tubes l0 and I5, including the lower portions of these tubes which extend along the inner vertically inclined walls forming the hopper bottoms of the furnace, will expand and contract with variations in temperature in the furnaces. Where equal or substantially equal temperatures prevail in both furnaces, the division wall and hopper bottom tubes will expand equally and will result in downward movement which is absorbed by the spring supports I0 and 4I. Upon contraction, the reverse action will take place. In the event furnace |1 is fired at a greater intensity than furnace Il, the division wall tubes il will absorb more heat than the division wall tubes i5, in consequence of which there will be a greater expansion of tubes Il than tubesy I5. As a result, channel members 04 will be moved downwardly against the action of springs 00, but as viewed in Fig. 2, the channels 04 will have a further counter-clockwise movement and will assume a horizontally inclined position. Also the header 01 will move downwardly farther than the header 00. Upon contraction, the reverse movements will occur. In the event furnace I0 is red at a greater intensity than furnace Il, tubes I including their lower portions which extend along the hopper bottom of the furnace, will move downwardly a greater distance than the tubes I4. In consequence, the channels I4 will move downwardly and additionally these channels will move in a clockwise direction so that eventually they assume a horizontally inclined position. At the same time header Il will move downwardly more than header 01. When the furnaces are shut down, reverse movements will take place.

From the foregoing it will be perceived that with the present invention the division wall tubes including their lower portions, will expand and contract pursuant to temperature conditions in the furnace, and that these division wall tubes may move together or relatively to each other either in expansion or in contraction, or in expansion of one group of tubes with contraction of the other group, or vice versa. Moreover. the tubes are adequately anchored so that they retain their positions irrespective of expansions and contractions.

Although the invention has been disclosed as applied to steam generators, it may be employed with vapor generators generally or in fluid heating apparatus. Moreover, the invention is applicable to furnaces having bottoms other than the hopper bottom type illustrated. It will be understood that changes may be made in the form, location and relative arrangement of the various parts of the apparatus disclosed herein without departing from the principles of the invention which is not to be limited excepting by the scope of the appended claims.

What is claimed is:

l. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for nring each furnace, means for separating the furnaces including rows of fluid conducting tubes, means for securing said tubes of one furnace to said tubes of the adjacent furnace in such a manner that the tubes can move axially relative to each other, and means for supporting` said separating means at least in part adjacent the lower end thereof. said last mentioned means being constructed and arranged te permit relative movement of the tubes of said rows resulting from expansion and contraction caused by different operating temperatures in said furnaces.

2. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a. plurality of furnaces in the setting, means for firing each furnace, a division wall between adjacent furnaces, fluid conducting tubes adjacent said division wall in each of said adjacent furnaces, means for securing said tubes of one furnace to said tubes of the adjacent furnace in such a manner that the tubes can move axially relative to each other, and means for supporting lthe division wall and said tubes at least in part adjacent the lower end thereof, said last named means being constructed and arranged to permit movement of the wall and the tubes resulting from expansion and contraction caused by operating temperatures in said adjacent furnaces.

3. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, a division wall between adjacent furnaces, iluid conducting -tubes adjacent said division wall in each of said adjacent furnaces. means for securing said tubes of one furnace to said tubes of the adjacent furnace in such a manner that the tubes can move axially relative to each other, and means for supporting the division wall and said tubes at least in part adjacent .the lower end thereof. said last named means being constructed and arranged to permit relative movement of the wall and the tubes resulting from expansion and contraction caused by different operating temperatures in said adjacent furnaces.

4. Fluid heating apparatus comprising a .setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of fluid conducting tubes, portions of said tubes of one row being vertically inclined in one direction, and portions of said tubes of another row being vertically inclined in an opposite direction to provide atleast in part adjacent bottom members for the furnaces sloping in opposite directions, and means for supporting said separating means at least in part adjacent said sloping bottom members and constructed and arranged to permit movement of the tubes of said rows resulting from expansion and contraction caused by operating `temperatures in said furnaces.

5. Fluid heating apparatus comprising a set ting, fluid heating tubes in the setting, a plurall ity of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of uid conducting tubes, portions of said tubes of one row being vertically inclined in one direction and portions of said tubes of another row being vertically inclined in an opposite direction to provide at least in part adjacent bottom members for the furnaces sloping in opposite directions, means for supporting said furnace separating means and said furnace bottom members adjacent said members including resilient means, and means for transmitting relative movement of said tubes resulting from expansion and contraction caused by operating temperatures in said furnaces to said resilient means.

6. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of fluid conducting tubes, portions of said tubes of one row being vertically inclined in one direction and portions of said tubes of another row being vertically inclined in an opposite direction to provide at least in part sloping bottoms for the furnaces, enclosing means associated with each of said sloping bottoms, means extending between said enclosing means and pivotally connected thereto, resilient means, means for supporting the resilient means, and means for pivotally connecting the resilient means to said means extending between said enclosing t means.

7. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces in- 8. Fluid heating apparatus comprising a setthe setting, a plurality ting, fluid heating tubes in means for firing each of furnaces in the setting,

furnace, means for separating the furnaces including rows of iuid conducting tubes, portions of said tubes of one row being vertically inclined in one direction and portions of said tubes of another row being vertically inclined in an opposite direction to provide at least in part sloping bottoms for the furnaces, enclosing means associated with each of said sloping bottoms, at least one link extending between said enclosing means and pivotally connected thereto, at least one coil spring, means for supporting the spring, means for pivotally connecting the link and the spring, and means permitting relative movement between the enclosing meansv and the supporting means for the spring.

9. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for nring each furnace, means for separating the furnaces including rows of fluid conducting tubes, a header with which the upper ends of the tubes are connected, means for supporting the header whereby -the tubes are suspended from the header, a header with which the lower ends of the tubes of each row of tubes are connected, means for independently and resiliently supporting each of said lower headers, and supporting means for said tubes positioned between the upper and lower ends of the tubes, said supporting means being independent of said header supporting means and constructed and arranged to permit relative movement of the tubes of said rows resulting from expansion and contraction caused by operating temperatures in said furnaces. y

10. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of fluid conducting tubes, portions of said tubes of one row being vertically inclined in one direction Iand portions of said tubes of another row being vertically inclined in an opposite direction to provide at least in part sloplng bottoms for the furnaces, a header with which the upper ends of the tubes are connected, means for supporting the header whereby the tubes are suspended from the header, a header with which the lower ends of the tubes of each row of tubes are connected, means for independently and resiliently supporting each of said lower headers, enclosing means associated with each of said sloping bottoms, a link extending between said enclosing means and pivotally connected thereto, a coil spring, means for supporting the spring, and means for pivotally connecting the link and the spring.

11. Fluid heating apparatus comprising a setting, uid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of fluid conducting tubes, and means for securing the tubes of one row to the tubes of another row to permit relative axial movement thereof, said securing means comprising an apertured lug welded to each tube, the lugs on one row of tubes being disposed at a different elevation than the lugs on the tubes of said other row with the apertures in vertical alignment, and pins extending through the vertically aligned apertures.

12. Fluid heating apparatus comprising a setting, iluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of duid conducting tubes, and

means for securing the tubes of one row to the tubes of another row to permit relative axial movement thereof, said securing means comprising an apertured lug welded to each tube, the lugs on one row of tubes being disposed at a different elevation than the lugs on the tubes of said other row with the apertures in vertical alignment, tie members associated with the lugs on each row of tubes, the tie members having apertures in alignment with the lug apertures and extending transversely of a plurality of tubes with the joints between the tie members at one elevation being staggered with respect to the joints between the other tie members, and pins extending through the vertically aligned apertures in the lugs and tie members.

13, A furnace having walls and a vertically inclined floor, uid conducting tubes for said inclined floor, and means for supporting the tubes on the floor to permit relative axial movement g of the tubes with respect to the floor comprising a lug secured to each tube, a plurality of blocks in the floor disposed in spaced relationship and located to receive said lugs in the spaces between the blocks, and means for maintaining said blocks in position in the floor.

14. A furnace having walls and a vertically inclined floor, fluid conducting tubes for said inclined floor, and means for supporting the tubes on the floor to permit relative axial movement of the tubes with respect to the floor comprising a lug secured to each tube, a plurality of blocks in the floor disposed in spaced relationship and located to receive said lugs in the spaces between the blocks, each block having an extension, and means engaging said block extensions for maintaining said blocks in position in the floor.

15. A furnace having walls and a vertically inclined floor, fluid conducting tubes for said inclined floor, and means for supporting the tubes on the floor to permit relative axial movement of the tubes with respect to the iloor comprising a lug secured to each tube, a plurality of blocks in the floor disposed in spaced relationship and located to receive said lugs in the spaces between the blocks, each block having an extension, and spaced channel members in engagement with opposite sides of said extensions for maintaining said blocks in position in the floor. 16. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of fluid conducting tubes, portions of said tubes of one row being vertically inclined in oneA direction, and portions of said tubes of another row being vertically inclined in an opposite direction to provide at least in par-t adjacent bottom members for the furnaces sloping in opposite directions, and means for supporting said separating means at least in part jacent said sloping bottom members and constructed and arranged to permit movement of the tubes of said rows in relation to one another resulting from expansion and contraction caused by operating temperatures in said furnaces.

17. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, a division wall between adjacent furnaces, uid conducting -tubes adjacent said division wall in 'each of said adjacent furnaces, means for securing said tubes of one furnace to said tubes of the adjacent furnace in a manner to permit relative axial movement between said fluid conducting tubes and prevent transverse movement of the tubes of each row and lateral movement of said rows in relation to each other, and means for supporting the division wall and said tubes at least in part yadjacent the lower end thereof, said last named means being constructed and arranged to permit movement of the wall and the tubes resulting from expansion and contraction caused by operating temperatures in said adjacent furnaces.

18. Fluid heating apparatus comprising a setting, uid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, a division wall between adjacent furnaces, fluid conducting -tubes adjacent said division wall in each of said adjacent furnaces. means for securing said tubes of one furnace to said tubes of the adjacent furnace in a manner to permit relative axial movement between said fluid conducting tubes and prevent transverse movement of the tubes of each row and lateral movement of said rows in relation to each other, and means for supporting the division wall and said tubes at least in part adjacent the lower end thereof, said last named means being constructed and arranged to permit relative movement of the wall and the tubes resulting from expansion and contraction caused by different operating temperatures in said ad lucent furnn ces.

19. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, meansfor firing each furnace, a division wall between adjacent furnaces, the division wall at the bottom thereof being divided, one portion thereof being vertically inclined in one direction and another portion thereof being vertically inclined in an opposite direction, fluid conducting tubes adjacent said division wall and the vertically inclined portions thereof, means for supporting the tubes on said inclined portions of the wall to permit relative axial movement of the tubes in respect to the inclined portions comprising a lug secured to each tube, a plurality of blocks in the inclined portions of the division wall disposed in spaced relationship and located to receive said lugs in the spaces between the blocks, means for maintaining said blocks in position in the inclined portions, and means for supporting said division wall and said tubes at least in part adjacent the lower end thereof, said last named means vbeing constructed and arranged to permit relative movement of the wall and the tubes resulting from expansion and contraction caused by different operating temperatures in said adjacent furnaces.

20. Fluid heating apparatus comprising a setting, fluid heating tubes in the setting, a plurality of furnaces in the setting, means for firing each furnace, means for separating the furnaces including rows of fluid conducting tubes, means for securing said tubes of one furnace to said tubes of the adjacent furnace in a manner to permit relative axial movement between said fluid conducting tubes and prevent transverse movement of each row and lateral movement of said rows in relation to each other. and means for supporting said separating means at least in part adjacent the lower end thereof, said last mentioned means being constructed and arranged to permit relative movement of the tubes of said rows resulting from expansion and contraction caused by different operating temperatures in said furnaces.

MARTIN FRISCH. 

